Extractive distillation process for separating the azeotropic distillate mixture of allyl alcohol and allyl acetate



Patented Mar. 14, 1950 "umren STATES PATENT. OFFlQlZ 2,500,596 7 EXTRAGTIVE DIS'I'ILLA'I'ION PROCESS AZEOTROPIC DISTIL- LATE MIXTURE OF ALLYL AND SEPARA'I'ING ALLYL ACETATE David E. Adelson, Berkeley, and Theodore W.

Evans, Oakland, Calif., alsignors to Shall Bevelopment Company, San Francisco, Calif., a corporation of Delaware Application April s, 1944, Serial No. 531.254

comma. (01. 202-395) invention relates to a process for separating the azeotropic mixture obtained as distillate upon distilling a beta,gamma-olefinic alcohol in admixture with a saturated monocarbcxylic acid ester of 'the'betagamma-oleflnic alcohol. More particularly, the invention pertains to an'extractive distillation rocess employing kerosene for separating the azeotropic distillate mixture of allyl alcohol and allyl acetate.

In this application, the term beta,gamma-'- olefinic alcoho is used to designates. class of unsaturated alcohols having an oleflnic, double bonded linkage between the two carbon atoms ture with monomer of a saturated monocarboxylic acid ester of the beta,gamma-oleflnic'alcohol,

which are 'in the beta and gamma positions with respect to the saturated carbon atom to which the hydroxyl group of the alcohol is directly attached.

In other words, the class of unsaturated alcohols with which the invention is concerned has an ole- .fl-nic linkage between two carbon atoms one of which is directly linked to a saturated carbon which ester contains not more than'12 carbon atoms, is separated by .contacting the azeotropic mixture in -a fractionating column with a normally liquid, non-polar hydrocarbon at a temperature above the boiling temperature of said monomeric alcohol, but below the boiling temperature of the hydrocarbon whereby the monomeric ester, substantially free of said monomeric alcohol, is absorbed in the hydrocarbon and vapors cpmprising monomer of the alcohol are evolved, the hydrocarbon having a normal boiling point at least 0. above the normal boiling point of the monomeric ester. The vapors evolved in this first operation are then separated from the ester-containing hydrocarbon and conatom having the hydroxyl group linked directly thereto. The lowest member of the beta,gammaolefinic alcohols is allyl alcohol. Illustrations of other members of the class will be given hereinafter.

As described in our copending application, Serial No. 425,118. filed December 31, 1941, now, U. 8. Patent No. 2,473,124, of which this application is a continuation-in-part, polyallyl alcohol is obtained from polyallyl acetate bv subjecting the polymeric ester to alcoholysis withmonomeric alester. The monomeric allyl acetate may be polymerized to polyallyl acetate which is the starting I material used in the alcoholysis process. It is, however, desirable that the monomeric ester be substantially free of monomericv alcohol when subjected to polymerization. The present inven-' tion provides a method for separating the suctropic mixture obtained by distilling allyl acetate in admixture with allyl alcohol as well as azeotropic mixtures of related lmsaturated alcohols and their esters.

According to the process of the present invention,.the azeotropic mixture obtained by distilling monomer of a beta,gamma-oleflnic alcohol containing not more than 8 carbon atoms in admixdensed. The ester-containing hydrocarbon 'is next distilled to iree, it oi ester and there is collected as distillate therefrom the desired monomeric ester substantially free of said monomeric alcohol. Thehydrocarbon obtained as residue from. this distillation step is substantially free of ester, and returned for contact again with the ester-alcohol azeotrope being separated in the flrst-mentio'ned-extractive.distillation. The condensed vapors from this extractive distillation comprising monomeric alcohol also contain some monomeric ester. After condensation and collection of these vapors. the condensate, if desired,

may be distilled whereby there is'obtained as distillate the azeotropic mixture of alcohol and ester, the residue being monomeric alcohol substantially free of ester. The azeotropic mixture collected in this additional distillation. may be returned to the extractive distillation for-contact again with the hydrocarbon..

The azeotropic mixture separated by the process contains a beta,gamma-oleflnic alcohol of not more than 6 carbonatoms and the corresponding saturated monocarboxylic acid ester of the alcohol. The alcohol can be either primary, secondary or tertiary, although primary alcohols are.

preferred. It is also preferred that the alcohol hols include such compounds as allyl alcohol,

have the carbon atomof a terminalmethylene group attached by an oleflnic double bond toa carbon atom which is directly attached to a saturated rcarbon atom having the hydroxyl group linked directly thereto. Representative specific examples of the most preferred subclass of alcomethallyl alcohol, ethallyl' alcohol, buten-l-ol-s, penten-l-ol-Zi, hexen-1-ol-3, 3-methylbuten-l- 01-3, 3-methylpenten-1-ol-3, 2-methylbuten-1-ol- 3, 2-methylpenten-l ol 3, 2,3-dimethylbuten-iazeotrope by extractive distillation using kerosene, the azeotrope being obtained by distilling thereaction mixture upon subjecting polyallyl acetate to ester-exchange alcoholysls with allyl alcohol to produce polyallyl alcohol.

In the drawing monomeric allyl alcohol from storage vessel II is conveyed by pipe I2 to pump I3 which discharges into line I4 having valve I5 therein and the allyl alcohol is charged to reactor 16 in which the ester-exchange reaction is efiected. The reactor is fitted with stirrer I1 and fractionating column I8 into which vapors are conveyed by conduit I3. Monomeric allyl acetate is conveyed from storage tank 2 I by line 22 having therein valve 23 to pressure pump 24. Pressure pump 24 discharges through line 25 into coil 26 of polymerization unit 21. The material in the coil is kept circulating by means of pipe 28 leading to circulating pump 29 which discharges back to lengthy nickel coil 26 through-pipe 36. The allyl acetate is admixed with about 2% nickel acetate as polymerization catalyst, and at the start of the operation, the allyl acetate is circulated through nickel coil as which is heated with hot oil to about 225 C. for about 2 to 3 hours. Polymerization unit 21 is then operated continuously by pumping allyl acetate into coil- 26 so that the residence time'therein is about 2 to 3 hours. The pressure supplied by pump 24 is suflicient to maintain the contents of coil 26 liquid, the pressure being regulated with pressure regulator valve 3|. The product from the polymerization operation is a mixture of monomeric allyl acetate and polyallyl acetate. The formed polymer-monomer mixture passes through valve 3| to line 32 through valve 33 and by line 34 to flash f ractionator 35 wherein the bulk of the unpolymerized allyl acetate is removed from the product of the polymerization treatment. Vapors from column 35 pass by line 36 to partial condenser 31 which provides reflux for operation of column 35. Uncondensed vapors of allyl acetate pass by line 38 to condenser and cooler 39 from which the condensate passes by line 46 through valve 4| to intermediate storage vessel 42. The residue from column 35 which contains the polyallyl acetate is removed through line 43 and valve 44 into line 45 passing tointermediate storage vessel 46. If desired, the intermediate fractionation of the product of polymerization is avoided in by-passing column 35 through closing of valves 33, 4| and 44 and opening valve 48 in line '41 whereby the crude polymer passes directly to vessel 46. The polyallyl acetate from vessel 46 is conveyed by pipe 5I to pump 52 which discharges through line 53 and valve 54 into reactor I6. Catalyst, consisting of sodium alloxide in solution with allyl alcohol, is transferred from vessel by line 56 through valve 51 to reactor I6. The contentsin reactor I6 are heated and boiled whereby the ester-exchange reaction giving monomeric allyl acetate and polyallyl alcohol occurs. The evolved allyl acetate along with allyl alcohol are fractionated in column I6 and distillate vapors consisting of the azeotropic mixture of those two compounds containing 37% allyl acetate and boiling at 95.1 C. pass by line 66 to partial condenser 6| which provides reflux for operation of the column. The allyl acetate is removed irom reactor I6 substantially as fast as formed by the ester-exchange reaction. The uncondensed azeotropic mixture from partial condenser 6| is conveyed by pipe 62 to condenser and cooler 63 from which the condensed distillate passes by line 64 to intermediate storage vessel 65. Upon completion of the ester-exchange reaction, the product remaining in reactor I6 is a solution of polyallyl alcohol 'in monomeric allyl alcohol plus the catalyst, sodium alloxide. This solution is dropped out of reactor I6 through line 66 by opening valve 61 and passed to vessel 66 which is packed with cation-exchange resin such as Amberlite IR-l which removes the catalyst.

The catalyst-free solution is conveyed by line 69 to pump 16 which discharges the solution through pipe I I to flash evaporator 12. Therein the monomeric allyl alcohol is vaporized from the polyallyl alcohol and the vapors pass by line 13 to partial condenser 14 thence through line I5 to condenser and cooler 16. The recovered allyl alcohol from condenser and cooler 16 is passed by line 11 to storage vessel II. The residue from column I2, consisting of polyallyl alcohol, flows by line I8 to storage vessel I9.

The azeotropic mixture of allyl acetate and allyl alcohol which accumulates in vessel 65 is separated by extractive distillation using a kerosene with a boiling range of about 200 C. to 235 C. as auxiliary solvent. This material is con- I tained in tank I26 from which it passes by line substantial amount of allyl acetate goes over-,

head. The temperature of the incoming kerosene must be kept below the normal boiling point of the allyl acetate. The azeotrope of allyl acetate and allyl alcohol is fed from tank 65 by line I26 to pump I 21 through pipe I28 to column I 25. Column I 25 is operated so that the ratio of kerosene to azeotropic feed is about 1:1 up to about 1:5. The bottom product is a mixture of kero 'sene and allyl acetate substantially free of allyl alcohol which is passed by line I29 to intermediate storage tank I36 from which it passes byline I3I to pump I32 which discharges through pipe I33 to'fractionating column I34. The vaporous product from column I34 consisting of pure, or substantially pure allyl acetate, passes by pipe I35 to partial condenser I36 which supplies reflux needed for operation of column I34. 'Uncondensed allyl cyclic system by being conducted thereto through line 59 to pump 24 upon opening valve 36 and closing valve 23. The residue from fractionator 134 is kerosene and is conveyed by line I 46 to tank I26 for recycling in the azeotrope. separation sys- -'I'he overhead product from column I25 will consist of allyl alcohol with a minor proportion 01 allyl acetate. Vapors of this material are conducted by line I to partial condenser I42 which supplies reflux for the rectifying section of colurnn I25. Partial condenser I42 is operated so that the reflux ratio is from about 1:1 up to about :1. The higher the ratio, the purer the allyl alcohol, although the purity is also dependent upon the kerosene to feed ratio. Uncondensed vapors from partial condenser I42 pass by line I43 to condenser and cooler I44 thence by line I45 to intermediate storage vessel I46. The allyl alcohol, containing a small amount of allyl acetate associated therewith, is conveyed from tank I46 by pipe I50 to pump I5I which discharges into line I52. Valve I64 is closed and valve I53 opened so that the material passes by line I54 to fractionating column I55. The distillate of vapors obtained in fractionator I55 is the allyl alcohol-allyl acetate binary azeotrope which passes by line I56 topartial condenser I51 which supplies reflux for column I55. Uncondensed vapors of the binary azeotrope pass by line I58 to condenser and cooler I59 from which the condensate passes by pipe I60 having valve I6I therein to tank 65 containing a minor amount of allyl acetate, from tank I46 can be conveyed directly to the allyl alcohol storage vessel II by,opening"valve I64 and passing it through pipe I65; in this case, column I55 is cut out of service by closing valves I53, I6I and I63. The allyl acetate conducted into the allyl alcohol charging stock passes to the estor-exchange unit from which it recirculates through the system. 1

While the process of the invention has been described and illustrated in the drawing with reference to producing polyallyl alcohol by means of allyl acetate and separating the formed alcohol-ester azeotrope by extractive distillation using kerosene, the process is suitable for application in producing other polymeric alcohols from monomeric beta,gamm'a-oleflnic alcohols containing not more than 6 carbon atoms by use of their saturated monocarboxylic acid esters containing not more than 12 carbon atoms. In place of kerosene, any normally liquid non-polar hydrocarbon which has a normal boiling point at least 20 C. above that of the monomeric ester can be used. In the extractive distillation method of separating the alcohol-ester azeotrope, the solvent does not appreciably vaporize in the fractionating column because of its higher boiling point. Since the solvent is separated from the ester with which it becomes associated by distilla- The kerosene can be refined kerosenewhich is substantially free of aromatics and is preferred to unrefined material containing appreciable amounts of aromatics.

The choice of the solvent requires exercise of 5 judgment. Thus, when using allyl formate (B. P. 83 0.), toluene (B, P. 111 C.) is suitable as solvent, but toluene cannot be used with allyl acetate (B. P. 104 C.) or methallyl isobutyrate' (B. P.

.omer of a saturated monocarboxylic acid ester of the beta, gamma-olefinic alcohol, said monomeric alcohol containing not more than 6 carbon atoms and said monomeric ester containing not more than 12 carbon atoms, which comprises contacting said mixture with a normally liquid, nonpolar hydrocarbon at a temperature above the boiling temperature of said monomeric alcohol, but below the boiling temperature of the hydrocarbon whereby said monomeric ester, substantially free of said monomeric alcohol, is absorbed in the hydrocarbon and vapors comprising monomer of said alcohol are evolved, said hydrocarbon having a normal boiling point at least 20 C. above the normal boiling point of said monomeric ester; separating said vapors and the ester-containing hydrocarbon; condensing said vapors; distilling the ester-containing hydrocarbon so as to obtain as residue substantially ester-free hydrocarbon; returning the ester-free hydrocarbon for contact again with ester-alcohol azeotrope; and collecting as distillate monomeric es'ter substantially free of said monomeric alcohol.

2. A process for separating the azeotropic mixture obtained by distilling monomer of a beta,-

gamma-olefinic alcohol in admixture with monotemperature of the kerosene whereby said monotion, a difierence of at least 20 C. between their meric ester, substantially free of said monomeric alcohol, is absorbed in said kerosene and vapors comprising monomer of said alcohol are evolved; separating said vapors and the ester-containing kerosene; condensing said vapors and. distilling the condensate whereby substantially ester-free alcohol is obtained as residue and azeotropic mixture of alcohol and ester is produced as distillate; returning the distillate for contact again with the kerosene; distilling the ester-contain ing kerosene so as to obtain as residue substantially ester-free kerosene; returning the esterfree kerosene for contact again with alcohol-ester azeotrope; and collecting as distillate substantially alcohol-free monomeric ester.

3. A process for separating the azeotropic mixture obtained by distilling allyl alcohol in admixture with allyl acetate which comprises contacting said mixture with a normally liquid, nonpolar hydrocarbon at a temperature above the boiling temperature of allyl alcohol, but below the boiling temperature of the hydrocarbon whereby allyl acetate substantially free of allyl alcohol is absorbed in the hydrocarbon and vapors comprissw m" ing allyl alcohol are evolved, said hydrggrbon having a normal boiling point at least C. above the normal boiling p6int of allyl acetatej separating said vapors and the ester-containing hydrocarbon; condensing said vapors; distilling the ester-containing hydrocarbon so as to obtain as residue substantially ester-free hydrocarbon; re-

turning the ester-free hydrocarbon for contact again with allyl alcohol-allyl acetate azeotrope; and collecting as distillate substantially allyl alcohol-free allyl acetate.

4. A process for separating the azeotropic mixture obtained by distilling allyl alcohol in admixture with allyl acetate which comprises contacting said azeotropic mixture with kerosene at a temperature above the boiling temperature of the alcohol, but below the boiling temperature of the kerosene whereby allyl acetatesubstantially free of alcohol is absorbed in the kerosene and vapors comprising allyl alcohol are evolved; separating said vapors and the ester-containing kerosene; condensing said vapors and distilling the condensate whereby substantially ester-free alcohol is obtained as residue and azeotropic mixture of alcohol and ester is produced as distillate; returning the distillate for contact again with the kerosene; distilling the ester-containing kerosene so as to obtain as residue substantially esterfree kerosene; returning the ester-free kerosene for contact again with alcohol-ester azeotrope; and collecting as distillate substantially alcoholfree allyl acetate.

5. A process for separating the azeotropic mixture obtained'by distilling allyl alcohol in admixture with allyl acetate which comprises contacting said azeotropic mixture with kerosene at a temperature above the boiling temperature of the alcohol, but below the boilin temperature of the kerosene whereby allyl acetate substantially free of alcohol is absorbed in the kerosene and vapors comprising allyl alcohol are evolved;,separating said vapors and the ester-containing kerosene; condensing said vapors; distilling the estercontaining kerosene so as to obtain as residue substantially ester-free kerosene; returning the ester-free kerosene for contact again with allyl acetate-allyl alcohol azeotrope; and collecting as distillate substantially allyl alcohol-free allyl acetate.

6. A process for separating the azeotropic mix ture obtained by distilling allyl alcohol in admixture with allyl fo'rmate which comprises contacting said mixture with a normally liquid, nonpolar hydrocarbon at a temperature above the boiling temperature of allyl alcohol, but below the boiling temperature of the hydrocarbon whereby allyl formate substantially free of allyl alcohol is absorbed in the hydrocarbon andvapors comprising allyl alcohol are evolved, said hydrocar bon having a normal boiling point at least 20 C. above the normal boiling point of allyl formate; separating said vapors and the ester-containing hydrocarbon; condensing said vapors; distilling the ester-containing hydrocarbon so as to obtain as residue substantially ester-free hydrocarbon; returning the ester-free hydrocarbon for contact again with allyl alcohol-allyl formate azeotrope;

and collecting as distillate substantially allyl alcohol-free allyl formate.

7. A process for separating the azeotropic mixture obtained by distilling allyl alcoholin admixture with allyl formate which comprises contacting said azeotropic mixture with kerosene at a temperature above the boiling temperature of the alcohol, but below the boiling temperature of the kerosene whereby allyl formate substantially free of alcohol is absorbed in the kerosene and vapors comprising allyl alcoholare evolved; separating said vapors and the ester-containing kerosene;

condensing said vapors and distilling the condensate whereby substantially ester-free alcohol isobtained as residue and azeotropic mixture of alcohol and ester is produced as distillate; return-' ing the distillate for contact again with the kerosene; distilling the ester-containing kerosene so as to obtain as residue substantially ester-free kerosene; returning the ester-free kerosene for contact again with alcohol-ester azeotrope; and collecting as distillate-substantially alcohol-free allyl formate.

- DAVID E. ADELSON.

THEODORE W. EVANS.

REFERENCES CITED The following references are of record in the file .of this patent:

Ryan et al., article in J. Am. Chem. Soc., 62, 3469 (1940). 

1. A PROCESS FOR SEPARATING THE AZEOTROPIC MIXTURE OBTAINED BY DISTILLING MONOMER OF A BETA,GAMMA-OLEFINIC ALCOHOL IN ADMIXTURE WITH MONOMER OF A SATURATED MONOCARBOXYLIC ACID ESTER OF THE BETA, GAMMA-OLEFINIC ALCOHOL, SAID MONOMERIC ALCOHOL CONTAINING NOT MORE THAN 6 CARBON ATOMS AND SAID MONOMERIC ESTER CONTAINING NOT MORE THAN 12 CARBON ATOMS, WHICH COMPRISES CONTACTING SAID MIXTURE WITH A NORMALLY LIQUID, NONPOLAR HYDROCARBON AT A TEMPERATURE ABOVE THE BOILING TEMPERATURE OF SAID MONOMERIC ALCOHOL, BUT BELOW THE BOILING TEMPERATURE OF THE HYDROCARBON WHEREBY SAID MONOMERIC ESTER, SUBSTANTIALLY FREE OF SAID MONOMERIC ALCOHOL, IS ABSORBED IN THE HYDROCARBON AND VAPORS COMPRISING MONOMER OF SAID ALCOHOL ARE EVOLVED, SAID HYDROCARBON HAVING A NORMAL BOILING POINT AT LEAST 20*C. ABOVE THE NORMAL BOILING POINT OF SAID MONOMERIC ESTER; SEPARATING SAID VAPORS AND THE ESTER-CONTAINING HYDROCARBON; CONDENSING SAID VAPORS; DISTILLING THE ESTER-CONTAINING HYDROCARBON SO AS TO OBTAIN AS RESIDUE SUBSTANTIALLY ESTER-FREE HYDROCARBON; RETURNING THE ESTER-FREE HYDROCARBON FOR CONTACT AGAIN WITH ESTER-ALCOHOL AZEOTROPE; AND COLLECTING AS DISTILLATE MONOMERIC ESTER SUBSTANTIALLY FREE OF SAID MONOMERIC ALCOHOL. 